CVE-2026-98223 mm: filemap: retain mapped dropbehind folios
A Linux kernel bug in filemap handling can cause a sleeping-in-atomic warning, potentially leading to system instability or denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98223?
CVE-2026-98223 is a denial of service vulnerability in Linux, published on 6 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
mm: filemap: retain mapped dropbehind folios
Fault-around can map ready dropbehind folios without going through the normal page-cache lookup that clears dropbehind. A mapping represents a competing cached user, so retain the folio instead of forcibly unmapping it when writeback completes.
For a mapped folio, folio_unmap_invalidate() can call unmap_mapping_folio(), which takes i_mmap_rwsem and may sleep. Retaining mapped folios avoids this path when folio_end_dropbehind() runs in non-preemptible task context.
Tal was able to trigger a sleeping-in-atomic warning due to this [1].
Unmapped dropbehind folios continue through the existing invalidation path.
Which versions are affected by CVE-2026-98223?
How do I fix CVE-2026-98223?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-98223 being exploited?
There is no known exploitation of CVE-2026-98223 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-98223, DEBIAN-CVE-2026-98223, GHSA-h9mh-jjx8-7v74, UBUNTU-CVE-2026-98223.